1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/**
* @file event_buffer.c
*
* @remark Copyright 2002 OProfile authors
* @remark Read the file COPYING
*
* @author John Levon <levon@movementarian.org>
*
* This is the global event buffer that the user-space
* daemon reads from. The event buffer is an untyped array
* of unsigned longs. Entries are prefixed by the
* escape value ESCAPE_CODE followed by an identifying code.
*/
#include <linux/vmalloc.h>
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/capability.h>
#include <linux/dcookies.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include "oprof.h"
#include "event_buffer.h"
#include "oprofile_stats.h"
DEFINE_MUTEX(buffer_mutex);
static unsigned long buffer_opened;
static DECLARE_WAIT_QUEUE_HEAD(buffer_wait);
static unsigned long *event_buffer;
static unsigned long buffer_size;
static unsigned long buffer_watershed;
static size_t buffer_pos;
/* atomic_t because wait_event checks it outside of buffer_mutex */
static atomic_t buffer_ready = ATOMIC_INIT(0);
/*
* Add an entry to the event buffer. When we get near to the end we
* wake up the process sleeping on the read() of the file. To protect
* the event_buffer this function may only be called when buffer_mutex
* is set.
*/
void add_event_entry(unsigned long value)
{
/*
* This shouldn't happen since all workqueues or handlers are
* canceled or flushed before the event buffer is freed.
*/
if (!event_buffer) {
WARN_ON_ONCE(1);
return;
}
if (buffer_pos == buffer_size) {
atomic_inc(&oprofile_stats.event_lost_overflow);
return;
}
event_buffer[buffer_pos] = value;
if (++buffer_pos == buffer_size - buffer_watershed) {
atomic_set(&buffer_ready, 1);
wake_up(&buffer_wait);
}
}
/* Wake up the waiting process if any. This happens
* on "echo 0 >/dev/oprofile/enable" so the daemon
* processes the data remaining in the event buffer.
*/
void wake_up_buffer_waiter(void)
{
mutex_lock(&buffer_mutex);
atomic_set(&buffer_ready, 1);
wake_up(&buffer_wait);
mutex_unlock(&buffer_mutex);
}
int alloc_event_buffer(void)
{
unsigned long flags;
spin_lock_irqsave(&oprofilefs_lock, flags);
buffer_size = oprofile_buffer_size;
buffer_watershed = oprofile_buffer_watershed;
spin_unlock_irqrestore(&oprofilefs_lock, flags);
if (buffer_watershed >= buffer_size)
return -EINVAL;
buffer_pos = 0;
event_buffer = vmalloc(sizeof(unsigned long) * buffer_size);
if (!event_buffer)
return -ENOMEM;
return 0;
}
void free_event_buffer(void)
{
mutex_lock(&buffer_mutex);
vfree(event_buffer);
buffer_pos = 0;
event_buffer = NULL;
mutex_unlock(&buffer_mutex);
}
static int event_buffer_open(struct inode *inode, struct file *file)
{
int err = -EPERM;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (test_and_set_bit_lock(0, &buffer_opened))
return -EBUSY;
/* Register as a user of dcookies
* to ensure they persist for the lifetime of
* the open event file
*/
err = -EINVAL;
file->private_data = dcookie_register();
if (!file->private_data)
goto out;
if ((err = oprofile_setup()))
goto fail;
/* NB: the actual start happens from userspace
* echo 1 >/dev/oprofile/enable
*/
return 0;
fail:
dcookie_unregister(file->private_data);
out:
__clear_bit_unlock(0, &buffer_opened);
return err;
}
static int event_buffer_release(struct inode *inode, struct file *file)
{
oprofile_stop();
oprofile_shutdown();
dcookie_unregister(file->private_data);
buffer_pos = 0;
atomic_set(&buffer_ready, 0);
__clear_bit_unlock(0, &buffer_opened);
return 0;
}
static ssize_t event_buffer_read(struct file *file, char __user *buf,
size_t count, loff_t *offset)
{
int retval = -EINVAL;
size_t const max = buffer_size * sizeof(unsigned long);
/* handling partial reads is more trouble than it's worth */
if (count != max || *offset)
return -EINVAL;
wait_event_interruptible(buffer_wait, atomic_read(&buffer_ready));
if (signal_pending(current))
return -EINTR;
/* can't currently happen */
if (!atomic_read(&buffer_ready))
return -EAGAIN;
mutex_lock(&buffer_mutex);
/* May happen if the buffer is freed during pending reads. */
if (!event_buffer) {
retval = -EINTR;
goto out;
}
atomic_set(&buffer_ready, 0);
retval = -EFAULT;
count = buffer_pos * sizeof(unsigned long);
if (copy_to_user(buf, event_buffer, count))
goto out;
retval = count;
buffer_pos = 0;
out:
mutex_unlock(&buffer_mutex);
return retval;
}
const struct file_operations event_buffer_fops = {
.open = event_buffer_open,
.release = event_buffer_release,
.read = event_buffer_read,
};
|
